Chain drive assemblies for work machines substantially comprise a crawler track which has a plurality of mutually connected hinged components or connections. Furthermore, at least one drive wheel and/or one guide wheel as well as a limited number of idler wheels are provided, with the crawler track being guided by each of the sprocket wheels.
To ensure the correct guidance of the chain on the sprocket wheels, the tension of the chain must be maintained during operation. A corresponding tensioning device which brings the chain to the desired tension level serves this purpose. A hydraulic cylinder or a helical spring which urge the front guide wheel of the chain drive assembly onto the chain to produce the desired chain tension serves as the tensioning device, for example. The applied pressure in the hydraulic cylinder determines the tension applied to the chain.
As the operating time increases, wear phenomena occur as a rule at the individual chain components, in particular at the connection points of the individual chain links, which results in a slackening of the chain tension and furthermore in a sagging of the chain. The excessive sag of the chain causes irregular wear of the individual chain components and can furthermore trigger a derailing of the chain guided on the sprocket wheels. To counter this phenomenon, it is necessary that the tension applied to the chain is regulated by the tensioning device as required.
Care must, however, be taken in this respect that an over-tensioning of the chain by the tensioning device is to be avoided. A chain which is set too tight can hugely restrict the durability of the chain in the long term since in this case the wear phenomena of the individual chain components which occur advance a lot faster.
Nevertheless, it can likewise be desirable that the chain tension is to be adapted to the respective working conditions of the work machine. It is thus desirable to tension the chain during working operation to a maximum tension level, whereas a chain tension reduced with respect to the maximum tension level is sufficient during transport operation and thus allows an optimization of the potential chain service life.
With known tensioning device such as hydraulic cylinders, the respective chain tension is determined by the pressure relationships in the hydraulic cylinder. In this respect it applies that the increase in the pressure level in the hydraulic cylinder has the consequence of an increase in the chain tension. This approach, however, requires expensive hydraulic components such as pressure limiting valves for pressure regulation.
It is therefore the object of the present invention to provide a simplified and improved design for a chain drive assembly. In particular an alternative approach for the implementation of a chain tensioning mechanism should be provided.
This object is achieved by a chain drive assembly for a work machine, having a drive crawler track, at least one displaceably supported sprocket wheel, and at least one tensioning device to tension the crawler track, wherein at least one abutment is provided which bounds the displacement of the displaceably supported sprocket.
In one particular example, a chain drive assembly for a work machine, in particular for a crawler-mounted crane or a crawler excavator, includes a drive crawler track, at least one displaceably supported sprocket wheel, in particular a guide wheel or idler wheel, and at least one tensioning device to tension the crawler track. The drive crawler track is guided over the sprocket wheel in a manner known per se. At least one sprocket wheel is displaceably supported, and indeed such that the displacement takes place in the direction of the chain on which the sprocket wheel lies, and the pressure of the sprocket wheel on the inner side of the chain is increased. The chain tension can be adjusted via the actuation of the tensioning device.
In accordance with the present disclosure, at least one abutment is provided which bounds the displacement of the displaceably supported sprocket wheel. The bounding of the displacement of the sprocket wheel takes place in the displacement direction increasing the chain tension. A displacement of the sprocket wheel in the opposite direction results in a reduction in the applied chain tension. An additional abutment can be provided which bounds the displacement of the displaceably supported sprocket wheel in the opposite direction.
Due to the abutment in accordance with the present disclosure, the tensioning device can act onto the displaceably supported sprocket wheel with a constant pressure. The maximum applied chain tension is bounded to a maximum value by the abutment. An overtensioning of the chain is prevented, which reduces the wear of the crawler track and optimizes its durability.
The abutment can be designed as adjustable. The adjustability of the abutment allows a variation of the applied chain tension. The displacement of the sprocket wheel generated by the tensioning device can consequently be limited to different maximum values.
The tensioning device can be designed as a known cylinder unit, in particular as a hydraulic cylinder unit. In the embodiment as a hydraulic cylinder unit, a constant pressure level can be applied at the hydraulic cylinder unit which presses the displaceably supported sprocket wheel towards the chain. The corresponding chain tension is not adjustable by pressure regulation, but by the abutment in accordance with the present disclosure. The pressure level of the hydraulic cylinder remains constant. Special hydraulic components such as a pressure limiting valve are no longer required. The hydraulic cylinder is acted on, for example, by a constant maximum pressure. The pressure of the sprocket wheel on the chain is only regulated via the abutment.
The displacement of the sprocket wheel for the configuration of the chain tension takes place in the direction of travel. Expediently, an outwardly disposed sprocket wheel, in particular the guide wheel, is displaceably supported. The displacement of the guide wheel takes place in the direction of travel away from the adjacent sprocket wheels so that the pressure on the inner side of the chain is increased. In this case, the displacement of the guide wheel or of the sprocket wheel in the direction of travel is bounded by the abutment in accordance with the present disclosure.
The fastening of at least one abutment takes place by a screw connection. The abutment can either be removed or attached in an offset manner by releasing the screw connection.
One or more boreholes are provided for receiving the screw connection in the region of the axial mount of the sprocket wheel. These bores are disposed in a distributed manner in the direction of travel with the same spacing or a varying spacing from one another so that the fixing of the abutment to one of the boreholes allows a defined maximum displacement of the sprocket wheel.
The present disclosure is furthermore directed to a work machine which has at least one chain drive assembly in accordance with one of the preceding features. The use of the chain drive assembly in accordance with the present disclosure at a crawler-mounted crane or a crawler excavator is particularly advantageous.
Further advantages and details of the present disclosure will be explained in more detail in the following with reference to the drawings.